In recent years, development in hybrid cars and electric automobiles is advancing, and various proposals have been made from the conventional mechanical hydraulic control to the electrical hydraulic control with respect to the braking of the vehicle.
A battery is generally used for a power source to electrically perform hydraulic control of the vehicle, but in this case, the hydraulic control cannot be performed with only the use of the battery if supply of power is terminated for some reason, and braking of the vehicle may become impossible.
A proposal has been made to respond to an emergency by mounting a plurality of large-capacity capacitors etc. as an emergency auxiliary power source separate from the battery.
Patent document and the like are known as prior art documents related to the present application. An example of a capacitor configuring one portion of a capacitor unit is shown in an exploded perspective view of FIG. 23. As shown in FIG. 23, two lead wires 602 arranged on one end face of each of plurality of capacitors 601 are bending worked to a crank shape. The vibration of the vehicle thus can be absorbed even when applied to lead wire 602, and thus breaking is less likely to occur, and reliability enhances. Capacitor 601 is still disassembled at the stage of bending working lead wire 602. Thus, although it is difficult to recognize in FIG. 23, the lengths of two lead wires 602 are differed from each other so that the polarity of lead wire 602 can be distinguished.
Capacitor 601 in which the preparation for bending work of lead wire 602 is completed is placed in each lead wire hole 604 formed in circuit substrate 603 while paying attention not to be mistaken the polarity. Although not shown in circuit substrate 603, a circuit component for electrically controlling capacitor 601 such as charging/discharging circuit and state detection circuit of capacitor 601 may be mounted in advance.
Capacitor 601 is then placed on holder 605 made of resin. Here, ribs and elastic portions are arranged inside the capacitor placement hole of holder 605, although not shown, and the body of capacitor 601 is held and fixed thereby.
After placing capacitor 601, four screws (not shown) are tightened to boss 607 integrally molded with holder 605 through circuit substrate screw hole 606 to fix circuit substrate 603 to holder 605.
Capacitor 601 and circuit substrate 603 are fixed to holder 605 at this point, and all the extra portions of two lead wires 602 which lengths are differed to distinguish the polarity are cut. Furthermore, two lead wires 602 of each capacitor 601 are all soldered to be electrically connected to circuit substrate 603.
As lead wire 602 is soldered after fixing capacitor 601 and circuit substrate 603 to holder 605, stress on the solder connected portion in time of assembly due to the soldering before fixation is not applied, and the reliability can be enhanced.
Lastly, moisture proof agent is formed on both surfaces of circuit substrate 603. The moisture proof agent is in liquid form, and is formed to a film-form after being hardened and thus is not shown in FIG. 23. The moisture proof agent has a function of preventing, in particular, short-circuit failure etc. due to attachment of moisture to the adjacent soldered portion. The moisture proof agent is thus formed so as to cover the soldered portion after all the soldering is finished. A severe in-vehicle environment then can be responded.
The method of forming the moisture proof agent on circuit substrate 603 is as described below. First, with respect to an upper surface side of circuit substrate 603 in FIG. 23, the assembled capacitor unit is turned upside down, and a lower surface (back surface in this case) of circuit substrate 603 is adhered to the liquid level in a liquid bath (hereinafter also referred to as moisture proof agent bath) filled with moisture proof agent. The moisture proof agent is thereby easily formed over the entire back surface of circuit substrate 603.
The entire capacitor unit can be immersed in the moisture proof agent to form the moisture proof agent on both surfaces of circuit substrate 603 all at once. However, if the moisture proof agent attaches to a bottom surface (surface with lead wire 602) of capacitor 601 mounted on circuit substrate 603, the bottom surface will corrode and capacitor 601 will break. Therefore, the method of immersing the entire capacitor unit in the moisture proof agent cannot be used.
When forming the moisture proof agent on a mounting surface (front surface) of capacitor 601 of circuit substrate 603, the moisture proof agent is applied with a dispenser etc. to the peripheral portion not mounted with capacitor 601 and the circuit components in circuit substrate 603, and thereafter, the capacitor unit is tilted to various angles and directions so that the moisture proof agent spreads over the entire front surface of circuit substrate 603. The moisture proof agent thus even forms at a central part of circuit substrate 603 where capacitor 601 is tightly packed.
The moisture proof agent is formed on both surfaces of circuit substrate 603 through the above steps, and the capacitor unit is completed.
The capacitor unit of such configuration can actually be used well as an auxiliary power source for vehicle braking from the aspects of vehicle vibration, enhancement in reliability of the soldered portion by moisture proof agent, and the like.
However, the formation of the moisture proof agent on the surface mounted with capacitor 601 of circuit substrate 603 is a complicated and difficult step. Furthermore, thickness of the moisture proof agent may vary after forming the moisture proof agent, and the configuration has an extremely bad productivity.
Moreover, since capacitor 601 is mounted in a vertical direction, the capacitor unit becomes higher or greater than or equal to the length of capacitor 601, and the installable location in a restricted vehicle space becomes limited. Therefore, miniaturization and lower height are necessary to enhance the degree of freedom of installation.    [Patent document 1] Unexamined Japanese Patent Publication No.